The ultimate goal of this project is to identify and characterize the neural mechanisms responsible for our perceptual abilities to attend to, and integrate, information from multiple sensory modalities. To this end, functional MRI will be used to investigate polymodal sensory and attentional interactions in the context of visual and auditory motion processing. For example, how does visual and auditory information about the motion of a passing care come together to yield a common percept? The pathways for visual motion processing in the human have been studied extensively and, recently, the auditory motion pathways have been under investigation. Together, these two separate lines of inquiry provide sufficient information to allow the two systems to be compared within individual subjects and, thereby, to investigate in detail how the two systems interact. The project has four specific aims. The first aim is to document the psychophysics of auditory motion perception, especially in the MRI environment. fMRI will then be used to delineate the cortical pathways involved in auditory motion perception. These pathways will be compared with the pathways activated during visual motion perception. A specific goal will be to identify sites where the two pathways converge to yield polymodal responses. The second aim is to identify interactions between the auditory and visual motion pathways resulting from the simultaneous presence of motion stimuli in each modality. Identifying sites where polymodal stimulation results in either enhancement or suppression compared to the unimodal response will be of particular interest. The third aim is to determine how task factors module the activity in the two motion pathways and in areas of convergence. The goal is to determine how the cortical activation patterns change when the subject must combine visual and auditory motion information in different ways to complete a task. The final aim is to identify the neural systems involved in control and allocation of attention to stimuli in the different modalities. The goal will be to determine if there are common or separate systems for controlling attention in each modality. Together, the results of these experiments will provide a detailed accounting of the brain systems responsible for the integration of auditory and visual motion information. Moreover, the comparison of the two motion systems will reveal more general principles governing the functional organization of all the sensory and attentional systems. These results will contribute directly to our understanding of the physiological basis of perceptual defects and attentional neglect resulting from brain pathology.